1. Field of the Invention
Embodiments of the present invention relate to a mammograph and a mammography process.
2. Description of the Prior Art
Mammography is a radiography technique for studying the breast of a patient for clinical and/or interventional purposes. It can especially detect early-stage breast cancer in a patient, and/or repair lesions leading up to surgical intervention.
FIG. 1 schematically illustrates a mammograph 50 in an embodiment known from the prior art. The mammograph 50 comprises a source 51 of X-rays capable of emitting a beam 52 of X-rays to a frame 53 comprising a lower block 54, on which the breast 56 of a patient rests, and an upper plate 55, a so-called compression pad. The upper plate 55 is mobile in vertical translation so as to compress the breast 56 of the patient against the lower block 54. The lower block 54 also comprises a detector 57, whereof the detection surface 58 is turned to the beam 52, directly below the breast 56. The beam 52 of X-rays emitted by the source 51 reaches the breast 56 of the patient, and the detector 57 then captures the X-rays transmitted by the breast 56 to take a mammographic image. As can be seen, the beam 52 of X-rays has a substantially conical form, generally rectangular in cross-section, whereof the apex is an emission focal spot located at the level of the source 51.
As is evident, for an image to be taken of the entire breast 56 of the patient it is necessary to have a distance between the detector 57 and the source 51 greater than a certain value to avoid parts of the breast being omitted in the image. Yet, the compactness of the mammograph 50 is especially characterised by the distance between the source 51 and the detector 57. As a consequence, prior art devices are not very compact.
The effect of bringing the source 51 closer to the detector 57 in the prior art mammographs would be to omit part of the breast 56 in the image. Also, X-rays are generally emitted from a metallic anode being impacted at an emission focal spot by a beam of electrons emitted by a cathode.
Increasing the size of the emission focal spot involves boosting the quantity of X-rays to be emitted throughout exposure of the detector to the rays. This is translated by a shorter acquisition time for a given quantity of X-rays reaching the detector, and therefore less risk of the breast moving during image acquisition, and ultimately improvement in the final image quality, which is interesting for the practitioner.
But a large-sized emission focal spot, associated with a small distance between the detector and the source, causes degradation of the image quality by the appearance of blurring in the prior art mammographs, apart from truncation of the breast in the image previously mentioned. In particular, visibility of some zones of interest, such as micro-calcifications, is degraded in the image. Prior art mammographs cannot therefore simultaneously reconcile compactness and image quality.
Also, as shown in FIG. 2, prior art mammographs require the use of a protective cover 59 for pushing back the head of the patient out of the image-taking zone, between the source and the detector. Indeed, in these mammographs the source is placed above or at the level of the head of the patient, along a vertical axis.
Due to the position of the patient under compression or to the pressure exerted by the protective cover on the patient, the breast of the patient tends to also be pushed back from the imaging zone, the disadvantage of which is to reduce the portion of the breast viewed by the mammograph, as well as creating a source of discomfort for the patient.
Embodiments of the present invention dispense with the above disadvantages